1. Technical Field
The present invention relates to a method for forming a hollow shaft and a product with a hollow shaft manufactured by the same. More specifically, the present invention relates to a method for forming a hollow shaft, which enables a hollow shaft with a flange to be directly formed in sheet metal by performing stamping (pressing) process on the sheet metal.
2. Related Art
Japanese Patent No. 3475551 discloses a method for forming a hollow shaft which protrudes from sheet metal by performing stamping process on the sheet metal. According to this Japanese Patent No. 3475551, the shaft can be formed in the sheet metal by way of stamping process which includes a first step of half-blanking the sheet metal based on stamping process and a second step of holding in a die the protruding portion obtained in the first step, putting a punch into the protruding portion, and pressing the protruding portion in an opposite direction to the direction of putting the punch into the protruding portion.
This type of metal-processed products is used in such a manner that the product with the shaft is attached to a certain member or a certain part is attached to the shaft. In this case, it is desired to prevent the attached product or part from being detached. However, the technique disclosed in the above-mentioned patent document 1 only forms a simple cylindrical shaft having a constant diameter. Accordingly, the usage of the shaft produced by this technique is seriously limited when the shaft is jointly utilized in combination with other members or parts.